Mold for forming a joint spacer device or a part thereof

ABSTRACT

A mold for forming a joint spacer device or a part thereof includes a rigid container body having a first perimeter profile delimiting a first molding surface configured to shape a first portion of the joint spacer or part thereof; and a rigid cover provided with a second perimeter profile delimiting a second molding surface configured to shape a second portion of the joint spacer or part thereof. The rigid container body and the rigid cover are removably engageable to each other, at the first and the second perimeter profile, so as to delimit a cavity corresponding to the external configuration of the joint spacer or part thereof. The mold includes a weakening system on the rigid container body and on the rigid cover, making them separable into parts to enable the extraction of the spacer device or part thereof, molded therebetween.

FIELD OF THE INVENTION

This invention relates to a mold for forming a joint spacer device or apart thereof, and a spacer device obtained with such a mold.

BACKGROUND OF THE INVENTION

Molds for joint spacer devices are known in the art and are usually madeof an elastically deformable material, such as, for example, silicone orother elastomeric suitable material. Those molds are adapted to befilled with bone cement supplemented with an antibiotic or othertherapeutic substance, when the latter is in the fluid and malleablemass phase, for the purpose of obtaining a finished spacer device.

The bone cement supplemented with the antibiotic or other therapeuticsubstance, after hardening, is subsequently removed from the mold andthe joint spacer thus obtained, after finishing off, is implanted in thejoint space of a patient to treat a disease in progress in the tissuessurrounding such joint space.

The molds in the prior art suffer from several drawbacks.

In the first place, being these made in elastically yielding-deformablematerial, such as silicone, they do not allow obtaining a spacer devicewith a definite shape in optimal manner, for which reason, onceextracted from the mold, a spacer device must be machined superficiallyand finished, in order to obtain the exact required shape.

These molds, furthermore, although being in most cases expected to bedisposed of/thrown away after only one single use, at times are reusedafter an appropriate washing process, for the purpose of reducing thecosts for obtaining spacer devices having the same shape.

It can happen, however, that such a washing does not remove completelyfrom the mold the traces of the antibiotic or additive therapeuticsubstance with bone cement used for a previous spacer device, with theresult that allergic reactions may occur in spacer devices made with anantibiotic to which a patient is not allergic, which was, however, madein a mold used previously with bone cement supplemented with anantibiotic to which the patient is allergic.

SUMMARY OF THE INVENTION

Therefore, it is the main object of the present invention to improve thestate of the art in the industry sector of molds for the forming ofjoint spacer devices or a part thereof.

It is another object of the present invention to provide a mold for theforming of a joint spacer device or a part thereof with an alternativeconfiguration with respect to traditional molds.

It is another object of the present invention to provide a mold for theforming of a joint spacer device or a part thereof that cannot be usedmore than once.

It is a further object of the present invention to provide a mold forthe forming of a joint spacer device or a part thereof, which does notrequire laborious finishing steps of the spacer extracted thereof.

It is still another object of the present invention to provide a moldfor the forming of a joint spacer device or a part thereof, which iseasy to make at competitive costs.

Not the least object of the present invention is that of providing ajoint spacer device or a part thereof obtained by means of such a mold.

According with an aspect of the present invention a mold is provided forforming a joint spacer device or a part thereof according to claim 1.

Dependent claims refer to preferred and advantageous embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present invention willbecome more evident from the detailed description of some examples ofpreferred embodiments of a mold for forming a joint spacer device or apart thereof, shown and described by way of example, but not limitedthereto, in the attached table of drawings wherein:

FIG. 1 is a plan view of a mold for forming a joint spacer device forthe hip-joint according to a first embodiment of this invention;

FIG. 2 shows a rear view of the mold of FIG. 1;

FIG. 3 illustrates a perspective view in side elevation of the mold ofFIG. 1;

FIG. 4 is a perspective view in side elevation of the mold of FIG. 1 inan intermediate position between an opening position and a closingposition;

FIG. 5 shows a detail of the mold of FIG. 1;

FIG. 6 is a plan view of a mold for forming a part of a joint spacerdevice for the joint of the knee according to a second embodiment of thepresent invention;

FIG. 7 shows a perspective view of the mold cover of FIG. 6;

FIG. 8 illustrates a perspective view of the mold container body of FIG.6;

FIG. 9 is a perspective view of the mold of FIG. 6 with container bodyand cover engaged with each other thereby delimiting a forming seat;

FIG. 10 shows another perspective view of the mold of FIG. 6, whereincontainer body and cover are engaged with each other;

FIG. 11 illustrates a perspective view in side elevation of a mold forforming a part of a joint spacer device according to a third embodimentof this invention;

FIG. 12 shows a plan view of the mold of FIG. 11;

FIG. 13 illustrates a perspective view of the container body of the moldof FIG. 11;

FIG. 14 is a perspective view of the cover of the mold of FIG. 11;

FIG. 15 shows a perspective view in front elevation of the mold of FIG.11, wherein the container body and the cover are in intermediateposition with the cover partly inserted in the container; and

FIG. 16 illustrates a perspective view of the mold of FIG. 11, whereinthe cover closes the container body and delimits with the latter theforming seat.

In the attached drawings equal parts or components are marked by thesame reference numerals.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

With reference to the attached figures, a mold according to thisinvention is generally indicated with number 1.

Mold 1, according to the present invention, is made in elasticallyundeformable plastic material, for example polyethylene, and,preferably, distinguishable by a high Shore A, comprised between 90 and150.

Mold 1, comprises at least a rigid container body 2 and at least a rigidcover 3, which can be coupled with each other to delimit a cavity 4corresponding to an external configuration of a joint spacer to beformed or a part thereof.

More particularly, the rigid container body 2 is provided with at leasta first perimeter profile 5, which internally delimits at least a firstmolding surface 6 intended to shape at least a first part of the jointspacer device. In different embodiments, the joint spacer device may bea hip spacer device or a tibial knee spacer device.

The rigid cover 3 is also provided with at least a second perimeterprofile 7, delimiting at least a second molding surface 8 intended toshape at least a second part of such joint spacer device.

The rigid container body 2 and the rigid cover 3 engage with each otherin a removable manner at the respective perimeter profiles 5 and 7, sothat the cavity 4 remains circumscribed therebetween.

With particular reference to FIGS. 1 to 5, which illustrate a mold forforming a joint spacer device according to a first embodiment of thisinvention, it will be noted that, in such a mold, the perimeter profile5 of the rigid container body 2 circumscribes a forming surface for alongitudinal half of a joint spacer device for hip, and the perimeterprofile 7 of the rigid cover 3 circumscribes a second molding surface 8for the other longitudinal half of such a spacer device.

Each molding surface 6 and 8 comprises a stem portion 9, 9′, a headportion 10, 10′, and a connection portion 11, 11′ between the stemportion and the head portion.

In the mold according to the first embodiment of the present inventionthe perimeter profiles 5 and 7 coincide with the access opening to thecontainer body 2 and the cover 3, respectively. across the accessopening it is possible to cast the bone cement supplemented with asuitable antibiotic, pouring it on the first molding surface 6 and onthe second molding surface 8, so as to cover them up to the level of therespective perimeter profile 5, 7.

According to a variation of the mold according to the invention, themolding surfaces 6 and 8 are each obtained in a respective support base12, 13, and each perimeter profile 5 and 7 extends substantiallyorthogonally from the respective base and away from it.

Between the upper end of each perimeter profile 5, 7 and the supportbase 12, 13 the mold according to the present invention comprises atleast an inclined plane perimeter wall 12 a, 13 a. The inclined planeperimeter walls 12 a, 13 a of the rigid container body 2 and of therigid cover 3, besides carrying out a stiffening function of therespective perimeter profile 5, 7, facilitate, in addition, the disposalof the bone cement poured in excess on the molding surfaces 6 and/or 8during the forming stage.

The mold according to the invention, as already mentioned above, isconfigured in such a manner that, once the bone cement is poured on themolding surfaces 6, 8 and after a certain time has passed for thepartial hardening thereof, the rigid container body 2 and rigid cover 3are engaged with each other and delimit a cavity 4 of finite size. Thebone cement therefore, which can be accidentally poured in excess on themolding surfaces 6 and/or 8, outflows sideways at the perimeter sectionsand it separates distinctly from the bone cement contained in the cavity4, thanks to the inclined plane perimeter walls 12 a and 13 a thatfacilitate its removal. It follows that, once the bone cement hascompletely hardened and it has been separated from the mold, as it willbe better said hereinafter, the hip spacer device thus obtainedcomprises a minimum perimeter edge (of width equal to the maximum ofthat of the perimeter profiles 5 and 7) and requires, therefore, minimumfinishing work before the implantation in situ.

For the removable type engagement between the rigid container body 2 andthe rigid cover 3, the mold according to the first embodiment of thisinvention comprises removable engagement means 14 of the male 15 andfemale 16 types.

Such removable engagement means 14 are provided in positions at, andalong, each perimeter profile 5, 7, so that, when the rigid containerbody 2 and the respective rigid cover 3 engage with each other at theirrespective perimeter profiles 5 and 7, the engagement between the maleengagement means 15 and the female engagement means 16 of the mold (see,in particular, FIG. 4) is also achieved.

According to a variation illustrated in the figures of the firstembodiment of this invention, the rigid container body 2 and the rigidcover 3 are hinged with each other at the respective bases 12, 13.

Each base 12, 13 can, furthermore, comprise a solid body made ofsuitable plastic material as described above, wherein the respectivemolding surface 6, 8 is hollowed out. Alternatively, it can compriseside walls 12 b, 13 b, delimiting at the top a base surface 12 c, 13 cfrom which the respective perimeter profile 5, 7 of the rigid containerbody 2 and the rigid cover 3 rise. In this case, each base 12 and/or 13can comprise, between the side walls, lower with respect to the rigidcontainer body 2 and/or the cover 3, one or more transversal stiffeningribs 17, so that the mold 1 according to the invention is elasticallyundeformable although being made with a reduced quantity of material.

Now, the mold 1 according to the first embodiment of the presentinvention comprises weakening means 18 on the rigid container body 2 andon the rigid covers 3, so that both the container body and the cover canbe separated in several parts in order to allow extraction of the spacerdevice that has been formed.

Such weakening means, illustrated schematically in the drawings,comprise at least a reduced thickness line (indicated merely by way ofexample in FIGS. 1 and 2 with dashed lines), at which the rigidcontainer body 2 and the rigid cover 3 can be separated in severalparts. Such a reduced thickness line is provided transversally and/orlongitudinally on both the rigid container body 2 and the rigid cover 3.

The mold 1 according to a second embodiment of the present invention,see in particular the annexed FIGS. 6 to 10, is particularly suitablefor forming a tibial portion of a spacer device for knee joint andcomprises at least a rigid container body 2 and at least a rigid cover3, which can be coupled with each other to delimit a cavity 4corresponding to the external configuration of such component or tibialpart.

More particularly, the rigid container body 2 of the mold according tothe invention has a substantially “C”-shaped plan configuration andcomprises a bottom wall 19 from which side walls 20 rise. The side walls20 end at the top with an edge 21, at an upper access opening 22.

The rigid container body 2 is provided with at least a first perimeterprofile 5, which upperly delimits at least a first molding surface 6intended to shape at least a first part of the joint spacer device.

The first perimeter profile 5 is defined by an internal shoulder at theside walls 20, at a distance substantially constant from the edge 21.

Also the rigid cover 3 has a substantially “C”-shaped plan configurationand is provided with at least a second perimeter profile 7, delimitingat least a second molding surface 8, intended to shape at least a secondpart of such joint spacer device.

The rigid container body 2 and the rigid cover 3 are engageable witheach other in a removable manner at their respective perimeter profiles5 and 7, so that the cavity 4 remains delimited therebetween.

As it will be noted, the bottom wall 19 of the rigid container body 2 ofthe mold 1 according to the second embodiment of the present inventionis substantially convex and has a central portion 19 a and two endportions 19 b and 19 c, at the free ends of the “C”. The central portion19 a is substantially in bas-relief with respect to the end portions 19b and 19 c.

Now, with reference to the rigid cover 3 of the mold of FIGS. 6 to 10,it will be noted how this has a lower surface 32, facing, in use, therespective rigid container body 2 and an outer surface 33, facing, inuse, externally. The rigid cover 3 comprises furthermore a perimeteredge 31 for the engagement with the edge 21 of the container body 2. Tothis regard, it will be noted that the cover has, at its lower surface32, a perimeter recess 34, within which the edge 21 of the rigidcontainer body 2 can be fit inserted, with interference. The edge 31 ofthe rigid cover 3 encloses externally the edge 21 of the container body2.

The second perimeter profile 7 of the mold according to the invention isprovided on the lower surface 32 of the rigid cover 3, which lowersurface 32 is partially insertable in the container body itself, withsuch perimeter profile 7 in abutment against the perimeter profile 5and, accordingly, with the internal shoulder of the container 2.

The rigid cover 3 of the mold according to the invention comprises alsoat least a through opening 35 for the overflow of the bone cementpossibly poured in excess in the rigid container body 2. Such a throughopening 35 also facilitates the overflow of air bubbles from inside thecavity 4.

The lower surface 32 of the rigid cover 3 comprises a central portion 32a, of substantially rectangular transversal section, extending away fromsuch lower surface 32, and facing, in use, the container body 2.

Now, also the mold 1 according to the second embodiment of the presentinvention comprises weakening means 18 both on the rigid container body2 and the rigid cover 3 (indicated in FIG. 6 merely as a way of examplewith dashed lines), so that they can both be separated in several partsin order to allow extraction of the spacer device formed therein.

Such weakening means, illustrated schematically in the drawing, compriseat least a reduced thickness line, at which the rigid container body 2and the rigid cover 3 can be separated in several parts. Such a reducedthickness line is provided with transversally and/or longitudinally bothon the rigid container body 2 and on the rigid cover 3.

The annexed FIGS. 11 to 16 show the mold for the forming of a jointspacer according to the third embodiment of the present invention, inparticular suitable for forming a component or femoral part of a kneejoint spacer device. Such a mold comprises at least a rigid containerbody 2 and at least a rigid cover 3, which can be coupled with eachother to delimit a cavity 4 (FIG. 16) corresponding to the externalconfiguration of such component or femoral part.

More particularly, the rigid container body 2 of the mold according tothe invention has a substantially “C”-shaped plan configuration andcircumscribes a bottom wall 19 from which side walls 20 rise. The sidewalls 20 end at the top with an edge 21 at an upper access opening 22.

The bottom wall 19 of the container body 2 of the mold 1 according tothe third embodiment of this invention is substantially concave and hasa central portion 19 a and two end portions 19 b and 19 c, at the freeends of “C”. The central portion 19 a is substantially in relief withrespect to the end portions 19 b and 19 c.

The rigid container body 2 is provided with at least a first perimeterprofile 5, which upperly delimits at least a first molding surface 6intended to shape at least a first part of the joint spacer device.

The first perimeter profile 5 is defined by an internal shoulder, at theside walls 20 of the rigid container body 2, at a not constant distancefrom the edge 21 and, therefore, from the bottom wall 19.

More particularly, the perimeter profile 5 of the container body 2 isclose to the edge 21 of the container itself at the free ends of the “C”(abutment portions indicated in the figures with the references 5 a and5 b) and at an opposite portion, intermediate with respect to such ends(indicated in the figures as 5 c). The perimeter profile 5 descendstowards the bottom wall 19 of the container body at the remaining endportions 19 b and 19 c, and at the portion of the side wall 20 comprisedbetween the free ends of “C” (stretch 5 d). The remaining portions ofthe perimeter profile 5 are continuous connection parts, since theperimeter profile 5 is continuous along the side wall 20 of thecontainer 2.

The rigid cover 3 has a substantially “C”-shaped plan configuration andis provided with at least a second perimeter profile 7, delimiting atleast a second molding surface 8, intended to shape at least a secondpart of such joint spacer device.

The rigid container body 2 and the rigid cover 3 are engageable in aremovable manner with each other at respective perimeter profiles 5 and7, so that the cavity 4 remains delimited therebetween.

Now, with reference to the rigid cover 3 of the mold of FIGS. 11 to 16,it will be noted how this has a lower surface 32, facing, in use, therespective rigid container body 2 and an outer surface 33, facing, inuse, externally. The rigid cover 3 comprises also a perimeter edge 31for the engagement with the edge 21 of the container body 2. To thisregard it will be noted that the rigid cover 3 has, at its lower surface32, a perimeter recess 34, within which the edge 21 of the rigidcontainer body 2 can be fit inserted, with interference. The edge 31 ofthe rigid cover 3 encloses externally the edge 21 of the container body2.

The second perimeter profile 7 of the mold according to the invention isprovided with on the lower surface 32 of the rigid cover 3, which can beinserted in the container body itself with the perimeter section 7 inabutment against the perimeter profile 5, i.e. with the internalshoulder of the rigid container 2. The second perimeter profile 7 of thecover is therefore configured in a corresponding manner to therespective perimeter profile 5.

The cover 3 of the mold according to the invention comprises also atleast a through opening (not illustrated in this case in the drawings)for the overflow of the bone cement cast possibly in excess in the rigidcontainer body 2. Such a through opening serves, as previously mentionedwith reference to the second embodiment of the present invention, tofacilitate the overflow of air bubbles from inside the cavity 4.

The lower surface 32 of the rigid cover 3 is substantially convex (seein particular FIG. 14) and comprises a central portion 32 a, recessedwith respect to the portions at the free ends of “C”. Such recessedportion 32 a is intended, in use, to be placed on top of the centralportion in relief 19 a of the container body.

Now, also the mold 1 according to the third embodiment of this inventioncomprises weakening means 18 both on the container body 2 and the cover3, so that both can be separated in several parts to allow extraction ofthe spacer device formed therebetween.

Such weakening means, illustrated schematically in the drawings by adashed line (for example in FIG. 12) comprise at least a reducedthickness line, at which the rigid container body 2 and the rigid cover3 can be separated in several parts. Such a reduced thickness line isprovided with transversally and/or longitudinally, both on the rigidcontainer body 2 and the rigid cover 3.

As for the other embodiments described above, the weakening means 18 areprovided with in such a position for which it is possible to extract thejoint spacer device or a part thereof from the mold without destroyingthe mold itself.

Now, with reference to the second and the third embodiment of thepresent invention, it will be noted that the rigid cover 3 can compriseat least a gripping portion 36, between the free ends of the said “C”.Such gripping portion facilitates the application of the rigid cover 3on the rigid container body 2, as well as their separation in severalparts thereof.

Both the rigid container body 2 and the rigid cover 3 can, furthermore,comprise at least a stiffening perimeter rib 37, so that they areelastically undeformable. Such rib is optional and, alternativelythereto, it can be envisaged to make the bottom of the container body 2or the cover with a greater quantity of material in order to providegreater stiffness to the mold.

Furthermore, once the rigid cover 3 is led to close the rigid containerbody 2, the mold can be kept closed by additional removable engagementmeans, not illustrated in the drawings, which comprise, for example,clamp engagement means, or clips or hooks, between the container body 2and the cover 3.

Once closed, with or without the aid of additional engagement means, themold can be laid on any of its surfaces, without the need to make itmaintain a precise position during hardening of the bone cement kepttherein.

The molds 1 described above are susceptible to several modifications andvariations within the protective scope of the claims that follow.

Thus, for example, if a joint spacer device were to be made for a hip bymeans of the mold according to the first embodiment of this invention,which joint device were equipped of a metal core or any other suitablematerial able to provide a greater resistance to forces of the spacerdevice, such mold would comprise also one or more spacer elements (notillustrated in the figures), for example sleeves fitted on such core orelement, in any case capable of supporting it, which could be positionedin a predefined position on one or the other molding surface 6 or 8 andwould allow keeping the core of the spacer suitably arranged in themold, during the forming phase of the joint spacer device.

The invention claimed is:
 1. A mold for forming a tibial knee spacerdevice or part thereof, comprising: a rigid container body provided witha first perimeter profile delimiting a first molding surface configuredto shape a first portion of the tibial knee spacer device or the partthereof; and a rigid cover provided with a second perimeter profiledelimiting a second molding surface configured to shape a second portionof the tibial knee spacer device or the part thereof, wherein the rigidcontainer body and the rigid cover are removably engageable with eachother, at the first and the second perimeter profile, so as to delimit acavity corresponding to an external configuration of the tibial kneespacer device or the part thereof, and wherein the mold furthercomprises weakening means on the rigid container body and on the rigidcover so that both the rigid container body and the rigid cover areseparable into parts to enable extraction of the tibial knee spacerdevice or the part thereof, molded therebetween.
 2. The mold accordingto claim 1, wherein the weakening means on the rigid container body andon the rigid cover comprise a line of reduced thickness, so that themold is separable into multiple portions at the line of reducedthickness.
 3. The mold according to claim 2, wherein the line withreduced thickness is provided transversally and/or longitudinally on therigid container body and on the rigid cover.
 4. The mold according toclaim 1, wherein the rigid container body has an edge delimiting a topaccess opening, and wherein the first perimeter profile is a shoulderlocated internally to the rigid container body.
 5. The mold according toclaim 4, wherein the rigid cover has a lower surface, an upper or outersurface, and a perimeter edge for engagement with the edge of the rigidcontainer body, and is configured so that the lower surface isinsertable in the rigid container body, with the second perimeterprofile in abutment against the shoulder.
 6. The mold according to claim5, wherein the second perimeter profile is provided on the lower surfaceof the rigid cover.
 7. The mold according to claim 5, wherein, on thelower surface of the rigid cover, a perimeter recess is defined, so thatthe edge of the rigid container body is configured to be fit inserted,with interference, in the perimeter recess.
 8. The mold according toclaim 5, wherein the rigid cover comprises a central portion having anessentially rectangular cross section, the central portion protrudingwith respect to the lower surface to face the rigid container body whenthe rigid cover engages the rigid container body.
 9. The mold accordingto claim 4, one or more through openings are defined in the rigid coverand enable an overflow of bone cement poured into the rigid containerbody in excess, the one or more through openings further facilitating anoverflow of air bubbles from the cavity.
 10. The mold according to claim4, wherein the shoulder is provided inside the rigid container body at asubstantially constant distance from the edge.
 11. The mold according toclaim 4, wherein the rigid container body has a plan configuration thatis essentially shaped as a “C” and comprises a bottom wall substantiallyconvex with a central portion and two end portions, the central portionbeing essentially in low relief with respect to the end portions. 12.The mold according to claim 4, wherein the rigid cover comprises atleast one gripping portion between free ends of the “C”.
 13. The moldaccording to claim 4, wherein the rigid container body a perimetricstiffening rib, causing the rigid container body to be elasticallyundeformable.
 14. The mold according to claim 1, further comprisingclamp-type additional removable engagement means between the rigidcontainer body and the rigid cover.